I installed ubuntu (18.04 lts) on my server along with Windows 10. It came to the part which said it is installed successfully and restart the system. After restarting the system, I am not able to choose an OS. Ubuntu is starting directly. I can see Ubuntu with 4 dots and a blank screen after that with blinking cursor for some time. After that the cursor stops blinking and the keyboard is also not working. I am not able to move the cursor too. Can someone please help me with this. I need it fixed asap and Ubuntu tech support is also not getting connected.